CA1107390A - Phased array antenna with reduced phase quantization errors - Google Patents
Phased array antenna with reduced phase quantization errorsInfo
- Publication number
- CA1107390A CA1107390A CA316,101A CA316101A CA1107390A CA 1107390 A CA1107390 A CA 1107390A CA 316101 A CA316101 A CA 316101A CA 1107390 A CA1107390 A CA 1107390A
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- Canada
- Prior art keywords
- phase
- elements
- wave energy
- energy signals
- coupling means
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
- H01Q3/30—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array
- H01Q3/34—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array by electrical means
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- Variable-Direction Aerials And Aerial Arrays (AREA)
Abstract
Docket R4069 PHASED ARRAY ANTENNA WITH
EAO:lhw REDUCED PHASE QUANTIZATION ERRORS
ABSTRACT OF THE DISCLOSURE
A phased array antenna includes a coupling network which is arranged to supply signals to pairs of elements located on opposite sides of the array center with a phase difference which is an odd-integral multiple of one-half the smallest phase step of the array phase shifters. This coupling network arrangement reduces antenna beam pointing errors which arise from a phase quantization of the array phase shifters.
EAO:lhw REDUCED PHASE QUANTIZATION ERRORS
ABSTRACT OF THE DISCLOSURE
A phased array antenna includes a coupling network which is arranged to supply signals to pairs of elements located on opposite sides of the array center with a phase difference which is an odd-integral multiple of one-half the smallest phase step of the array phase shifters. This coupling network arrangement reduces antenna beam pointing errors which arise from a phase quantization of the array phase shifters.
Description
BACKGROUND OF THE INVENTION
This invention relates to phased array antenna systems, and particularly to such systems wh~ch are used for direction finding applications.
Figure 1 illustrates a typical prior art phased array antenna system. Wave energy signals from a transmitter 11 are supplied to antenna elements by coupling network 13.
The phase of signals supplied to each element 10, 12, 12', 14, .
, :
, ,~,., i,~ c~- .
~2~`
:
~ :::
~ t~ 3 14', 16, 16', 18, and 18' i5 nominally the same. Phase shifters 20, 22, 22', 24, 24', 26, 26', 28, and 28', each associated with one of the elements, are provided for varying the phase of wave energy signals, thereby to change the direction of the antenna beam radiated from the antenna.
Since the antenna is fully reciprocal, transmitter 11 may be replaced with a receiver, and the phase shifters used to change the direction from which signals are received.
The phase shifters used 1n the antenna of Figure 1 are typically digital phase shifters such as illustrated in Figure lA. The Figure lA phase shifter is a 3-bit phase shifter, which may typically be a diode or ferrite device.
The phase shifter includes bit 15 or changing input phasP
; by 1~0, bit 17 for changing phase by ~0, and bit 19 for changing phase b~ 45. Those f~miliar with suc~ phased array antenna systems will understand that such digital phase shifters may have a larger or smaller number of bits, ~ and that the bits are switched "on" or "off" by phase control `~ signals to change the phase of supplied signals to approximate the desired phase. This approximation i5 more accurate if a larger number of "bits" are provided in the phase shifter.
Figure 2 is a graph illustrating the ideal phase of wave energy signals to be supplied to the eIements of the Figure 1 array ln order to steer the antenna beam to a selected radiation scan angle ~,indicated in Figure 1.
For convenienc:e, the required phase ~or each element is referenca to t:he phase at central element 10, and plotted as a function of sine ~ so that the phase functions are linear. It should be recognized that the phase values . ;
~3 :
23;~20 J~t~
illustrated may be referenced to any particular phase value, or to the phase supplied to any particular element. The phase of element 10 has been selected as a reference phase merely for convenience.
Since the phase shifter of Figure lA cannot assume all values o phase change, in order to steer the antenna beam, it is necessary to set the phase bits 15, 17, and 19 to approximate the phase conditions illustrated in Figure 2.
Figure 3 is a graph illustrating the phase of wave en~rgy signals to be supplied to elements 14 and 14', which are symmetrically located in the array with respect to the array center. The graph illustrates only phase values for positive scan angles, and again, for convenience, phase values are plotted against the sine of the scan angle ~. The stepped lines in the graph illustrate the values which will be as~med by phase shifters 24 and 24' in order to approximate the required phase function at various antenna scan angles. From the graph, it is svident that the phase difference between the values of phase shifters 24 and 24' is not always the same as the ideal phase difference for perfect beam scanniny. The di~Eerence between the ideal and actual phase differencs is phase error , which results in a pointing error in the radiated antenna beam. Figure 4 is a graph illustrating the variation in the phase error for elements 14 and 14' .
as a function of the sine of the scan angle~ This phase error has a maximum amplitude of + 45 assuming 3-bit phase shifters. While it should be recognized that the presence of many elements in a phased array antenna tends to reduce the effect of this '~
~ ~4~
phase error, which arises from phase quantization, there will remain some inaccuracies in the steering direction of the array antenna as a result of the phase error in the phase difference between elements on opposite sides of the array center.
The antenna beam pointing error, which arises from phase quantization is relatively small and unimportant in many systems. In a high accuracy direction finding system, such as a microwave landing system or tracking radar, the phase quantization beam pointing error may be significant. It is also desirable to reduce phase ~uantization errors because the error may increase antenna sidelobes, an undesired effect in certain applications.
- It is therefore an objec~ of the present invention to provide an improved phased array antenna system having reduced phase quantization error.
SUMMARY OF THE INVEN~ION
In accordance with the invention, there is provided a phased array antenna system ha~ing a plurality o antenna element pairs arra~ged on an aperture~ The elements of each pair are oppositely located with respect to a plane passing through the aperture. Coupling means are provided ~or supplying wave energy siynals to the elements. ~he coupling mean~s include digital phase shifters for varying the phase o khe wave energy signals in discrete phase steps. The phase length o~ the coupling means is selected so that wave energy signals, supplied ~o the eIements in ': :
~5 ~ 23220 each pair, have a phase difference which is always approximately an odd-in~egral multiple of one-hal~ the smallest phase step of the phase shifters.
The elements are preferably located s~metrically with respect to a plane which passes through the center of the aperture. The phase shiftexs are preferably responsive to phase control signals, which cause the phase of wave energy signals supplied to each element to be approximately a predetermined function of the desired antenna radiation angle.
For a ~etter understanding of the present invention, together with other and further objects, reference is made to the following description, taken in conjunction with the accompanying drawings, and its scope will be pointad out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Figuxe 1 is a schematic diagram of a phased array antenna sys*em in accordance with the prior art.
Figure 1 A is a block diagram of a digital phase shifter.
~igure 2 i5 a graph illustratin~ phase functions for the elements of the Figure 1 antenna plotted against the :: .
sine of the radiation~angle.
Figure 3 is a~ graph illustrating phase quanti~ation for the el~nents o~ the Figure 1 antenna.
F:igure 4 is~a graph illus~rating phase errors as a result of phase quantization for two elements in a pair.
::: : : :
:~ :
6~
, ~
~:
~ 3~ 23220 Figure 5A is a schematic diagram of an antenna in accordance with the present in~ention.
Figure 5B is a sc~ematic diagram of another antenna in accordance with the present invention.
Figure 6 is a graph illustrating phase quantiza-tion or two elements of the Figures 5A and 5B antennas.
Figure 7 i8 a graph illustrating phase errors as a result of phase quantization for the Figures 5~ and 5B
antennas.
Figure 8 is a block diagram illustrating apparatus for providing phase control signals to the phase shifters of the Figure 1, Figure 5, and Figure 9 antennas.
Figure 9 is a schematic diagram of an antenna system in accordance with the present invention which is provided with antenna element intercoupling.
.
DESCRIPTION OP TH~ INYEN~ION
Figures SA and 5B illustrate antennas constructea in accordance with the present invention. In each case, antenna eIements are grouped in pairs of elements which are oppositely located with respect to the center o the array aperture. In the Figure 5A a~tenna, which has an odd number of elements, element 30 is unpaired, but elemenks 32, 34, 36, and 38 are paired with eIements 3~', 34', 36i, and 38', respectively, which are oppositely located on a plane with respect to a perpendicular plane~35 at the array center.
Coupling network 33 supplies signals to the elements from transmitter 31. One of the elements in each pair is provided .~
~ 7~;
3~ 3 23220 with a fixed phase adjustment in the coupling network, such as phase adjustments 41, 43, 45, and 47. The phase adjustments have a magnitude of one-half the value of the smallest bit in the phase shifters 40, 42, 42', 44, 44', 46, 46', 48, 48' of the array. Thus, if the array is provided with 3-bit phase shifters, such as that illustrated in Figure lA, phase adjustments 41, 43, 45, and 47 will haYe a value of 22.5.
In the Figure 5A antenna the phase adjustments are provided on alternate adjacent elements so that each element without a phase adjustment has at least one adjacent element with a phase adjustment provided in the coupling network.
The Figure 5B array has an even number of elements :~ 52, 52l, 54, 54', 56, 56', 58, 58' and cons.equently there is no unpaired central element. ~ikewise, the Figure 5B antenna is provided with coupling network 53 connecting the ~lements to transmitter 51. The coupling network includes phase shifter 62, 62', 64, 64', 66, 66', 68, and 68'. Unlike the Figure ~; 5A antenna~ all of the phase adjustments 61 r 63~ 65, 67 are ~: provided at the elements on the lower half of the array. As ~: 20 is k.nown to those famillar with the art, the ideal phase difference unction between elements in a pair, for example, pair 34, 34' of the Figure 5A antenna and pair 54, 54' of .
; . the Figure SB antenna is dependent on the space L between : the elements, as well as the`desired scan angle ~. For purposes of explaining the operatlon of the invention, i~ will be assumed that there is equal spacing L be~ween element pairs 34, 34' and 54, 54' so that there~is. idealIy the same : phase difference between signals suppliea to these elements for any particular antenna radiation angle.
~ 3i~r~ 23220 While the phase adjustments in Figures 5A and 5B
are illustrated as being arranged between the antenna element and the phase shifter, those familiar with the art will recognize ~hat the phase adjus~tments may be located at any point in the antenna coupling network provided the required phase difference exists at the antenna radiating element.
Likewise, those familiar with the art will recognize that the phase adjustment may have a phase magnitude e~ual to an odd integral multiple of one-half the smallest phase step of the digital phase shifter, and that th~ digital phase shiter may be appropriately controlled to remove any excess phase difference inisteps of its smallest bit. According to ; either arrangement, the elements are arranged in two groups, thosewith and those without the phase adjustments. The elements of any group always have a phase, with respect to the other elements in the same group, which is an integral multiple of the smallest phase shifter bit. The eleme~ts always have a phase, with respect to the eIements in the other group, which is an odd-integral multiple o one-half the smallest phase shifter bit.
: ~ Pigure 6 illustrates the ideal phase function for ~: ~ elements 34 and 34' of the Figure 5A antenna, which are the same as:the ideal phase functions for elements 54 and 54' of the Figure 5B antenna, because of the assumption of equal element spacing L. The ideal functions are identlcal to the ideal : functions for corresponding:elements l4 and 14'~of the : Figure l antenna.
The step functions in Flgure 6 illustrate the~digital phase approximations for phase shifters 44 and 44' to the 9-~
: ~
7Z~ 23220 ideal phase ~nction,which take into account the fixed phase difference introduced by phase adjustment 45. As compared to the graph of Figure 3, it will be seen that phase shifter 44' is switched at different intervals of scan angle ~ to S approximate the ideal function. This di~ference is the result of the presence of phase adjustment 45. The fact that phase shifter 44' is changed at different scan angles than phase shifter 44 results in a reduction in the magnitude of the phase error arising out of phase quantization. In this respect, it should be noted that the ~uantized phase function for each of the elements has the sam sense of displacement from the ideal function. Consequently, the difference between ; the actual quantized phase values is closer to the ideal phase difference. Figure 7 illustrates the phase quantization error ~' between elements 44 and 44' of the Figure 5A antenna, which is the same as the quantization error between eLements 54 and 54' o~ the Figure 5B antenna. From the graph, it may be seen that the maximum error is one-ha1f the smallest phase shifter bit or 22.5 not 45,which resuLted from the prior ~o art arrangement o~ Figure l.
Figure 8 illustrates apparatus for providing .
phase control signals t~ the phase~shifters of an array antenna. A beam selection device 90 provides output signals, for example logic signals repreaentative of the desired antenna beam pointing direction. These logic signals are i provided~as alddress inputs to read-only memories 92, 94, 96, and 98 (ROM's). The read-on~y memories are each programmed to provide the phase-shift control signals to one of the phase shifters of the array. In accordance with the invention, ~: :
~la~
~ ~ 23220 the memories must be progra~ned to take into account the presence of the phase adjustments in the antenna coupling network. It will be recognized that the required phase control signals may be provided by other devices, such as programmed microprocessors or special purpose computer circuits.
Figure 9 illustrates an application Oæ the invention to an antenna system wherein coupling means 75 are provided ~or interconnecting the element groups 72, 72', 74, 74', 76, 76', 78, and 78' of the array to varuous signal input ports 77 according to the prior U. S. Patent No. 4,041,501 to Frazita, et al. The coupling netowrk 73 connects trans-mitter 71 with ports 77 and includes phase s~ifters ~2, 82', 84, 84', 86, ~6', 88, and 88' as well a~ phase adjus~ments 81, 83, 85, and 87. The use o~ the present invention is of par~icular advantage in this type o array, because the large effective element spacing d', ~hich results from the use o ; the element intercouplin~ network, renders the antenna more susceptible to phase quntization pointing errors than con-ventional phased array antannas with a phase shifter for each individual element.
Computer calculations of antenna pointing errors for an antelma o~ the type illustrated in Figure 9 having 24 4 bit phase shifters have been mada. For the antenna without the phase adjustments according to the 1nvention,a2sigma pointing error of 0.011 deyrees was calculated. When phase adjus1~ments on both sides of the array center, in the configuration of Figure 5~, are provided the 2 sigma pointing ,: :
~11 :
~ {~ 23220 error from phase quantizatiorl is reduced approximately to 0.004 degrees. Phase adjustments on only one sidP of the array center, in the configuration of Figure 5B xeduced the
This invention relates to phased array antenna systems, and particularly to such systems wh~ch are used for direction finding applications.
Figure 1 illustrates a typical prior art phased array antenna system. Wave energy signals from a transmitter 11 are supplied to antenna elements by coupling network 13.
The phase of signals supplied to each element 10, 12, 12', 14, .
, :
, ,~,., i,~ c~- .
~2~`
:
~ :::
~ t~ 3 14', 16, 16', 18, and 18' i5 nominally the same. Phase shifters 20, 22, 22', 24, 24', 26, 26', 28, and 28', each associated with one of the elements, are provided for varying the phase of wave energy signals, thereby to change the direction of the antenna beam radiated from the antenna.
Since the antenna is fully reciprocal, transmitter 11 may be replaced with a receiver, and the phase shifters used to change the direction from which signals are received.
The phase shifters used 1n the antenna of Figure 1 are typically digital phase shifters such as illustrated in Figure lA. The Figure lA phase shifter is a 3-bit phase shifter, which may typically be a diode or ferrite device.
The phase shifter includes bit 15 or changing input phasP
; by 1~0, bit 17 for changing phase by ~0, and bit 19 for changing phase b~ 45. Those f~miliar with suc~ phased array antenna systems will understand that such digital phase shifters may have a larger or smaller number of bits, ~ and that the bits are switched "on" or "off" by phase control `~ signals to change the phase of supplied signals to approximate the desired phase. This approximation i5 more accurate if a larger number of "bits" are provided in the phase shifter.
Figure 2 is a graph illustrating the ideal phase of wave energy signals to be supplied to the eIements of the Figure 1 array ln order to steer the antenna beam to a selected radiation scan angle ~,indicated in Figure 1.
For convenienc:e, the required phase ~or each element is referenca to t:he phase at central element 10, and plotted as a function of sine ~ so that the phase functions are linear. It should be recognized that the phase values . ;
~3 :
23;~20 J~t~
illustrated may be referenced to any particular phase value, or to the phase supplied to any particular element. The phase of element 10 has been selected as a reference phase merely for convenience.
Since the phase shifter of Figure lA cannot assume all values o phase change, in order to steer the antenna beam, it is necessary to set the phase bits 15, 17, and 19 to approximate the phase conditions illustrated in Figure 2.
Figure 3 is a graph illustrating the phase of wave en~rgy signals to be supplied to elements 14 and 14', which are symmetrically located in the array with respect to the array center. The graph illustrates only phase values for positive scan angles, and again, for convenience, phase values are plotted against the sine of the scan angle ~. The stepped lines in the graph illustrate the values which will be as~med by phase shifters 24 and 24' in order to approximate the required phase function at various antenna scan angles. From the graph, it is svident that the phase difference between the values of phase shifters 24 and 24' is not always the same as the ideal phase difference for perfect beam scanniny. The di~Eerence between the ideal and actual phase differencs is phase error , which results in a pointing error in the radiated antenna beam. Figure 4 is a graph illustrating the variation in the phase error for elements 14 and 14' .
as a function of the sine of the scan angle~ This phase error has a maximum amplitude of + 45 assuming 3-bit phase shifters. While it should be recognized that the presence of many elements in a phased array antenna tends to reduce the effect of this '~
~ ~4~
phase error, which arises from phase quantization, there will remain some inaccuracies in the steering direction of the array antenna as a result of the phase error in the phase difference between elements on opposite sides of the array center.
The antenna beam pointing error, which arises from phase quantization is relatively small and unimportant in many systems. In a high accuracy direction finding system, such as a microwave landing system or tracking radar, the phase quantization beam pointing error may be significant. It is also desirable to reduce phase ~uantization errors because the error may increase antenna sidelobes, an undesired effect in certain applications.
- It is therefore an objec~ of the present invention to provide an improved phased array antenna system having reduced phase quantization error.
SUMMARY OF THE INVEN~ION
In accordance with the invention, there is provided a phased array antenna system ha~ing a plurality o antenna element pairs arra~ged on an aperture~ The elements of each pair are oppositely located with respect to a plane passing through the aperture. Coupling means are provided ~or supplying wave energy siynals to the elements. ~he coupling mean~s include digital phase shifters for varying the phase o khe wave energy signals in discrete phase steps. The phase length o~ the coupling means is selected so that wave energy signals, supplied ~o the eIements in ': :
~5 ~ 23220 each pair, have a phase difference which is always approximately an odd-in~egral multiple of one-hal~ the smallest phase step of the phase shifters.
The elements are preferably located s~metrically with respect to a plane which passes through the center of the aperture. The phase shiftexs are preferably responsive to phase control signals, which cause the phase of wave energy signals supplied to each element to be approximately a predetermined function of the desired antenna radiation angle.
For a ~etter understanding of the present invention, together with other and further objects, reference is made to the following description, taken in conjunction with the accompanying drawings, and its scope will be pointad out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Figuxe 1 is a schematic diagram of a phased array antenna sys*em in accordance with the prior art.
Figure 1 A is a block diagram of a digital phase shifter.
~igure 2 i5 a graph illustratin~ phase functions for the elements of the Figure 1 antenna plotted against the :: .
sine of the radiation~angle.
Figure 3 is a~ graph illustrating phase quanti~ation for the el~nents o~ the Figure 1 antenna.
F:igure 4 is~a graph illus~rating phase errors as a result of phase quantization for two elements in a pair.
::: : : :
:~ :
6~
, ~
~:
~ 3~ 23220 Figure 5A is a schematic diagram of an antenna in accordance with the present in~ention.
Figure 5B is a sc~ematic diagram of another antenna in accordance with the present invention.
Figure 6 is a graph illustrating phase quantiza-tion or two elements of the Figures 5A and 5B antennas.
Figure 7 i8 a graph illustrating phase errors as a result of phase quantization for the Figures 5~ and 5B
antennas.
Figure 8 is a block diagram illustrating apparatus for providing phase control signals to the phase shifters of the Figure 1, Figure 5, and Figure 9 antennas.
Figure 9 is a schematic diagram of an antenna system in accordance with the present invention which is provided with antenna element intercoupling.
.
DESCRIPTION OP TH~ INYEN~ION
Figures SA and 5B illustrate antennas constructea in accordance with the present invention. In each case, antenna eIements are grouped in pairs of elements which are oppositely located with respect to the center o the array aperture. In the Figure 5A a~tenna, which has an odd number of elements, element 30 is unpaired, but elemenks 32, 34, 36, and 38 are paired with eIements 3~', 34', 36i, and 38', respectively, which are oppositely located on a plane with respect to a perpendicular plane~35 at the array center.
Coupling network 33 supplies signals to the elements from transmitter 31. One of the elements in each pair is provided .~
~ 7~;
3~ 3 23220 with a fixed phase adjustment in the coupling network, such as phase adjustments 41, 43, 45, and 47. The phase adjustments have a magnitude of one-half the value of the smallest bit in the phase shifters 40, 42, 42', 44, 44', 46, 46', 48, 48' of the array. Thus, if the array is provided with 3-bit phase shifters, such as that illustrated in Figure lA, phase adjustments 41, 43, 45, and 47 will haYe a value of 22.5.
In the Figure 5A antenna the phase adjustments are provided on alternate adjacent elements so that each element without a phase adjustment has at least one adjacent element with a phase adjustment provided in the coupling network.
The Figure 5B array has an even number of elements :~ 52, 52l, 54, 54', 56, 56', 58, 58' and cons.equently there is no unpaired central element. ~ikewise, the Figure 5B antenna is provided with coupling network 53 connecting the ~lements to transmitter 51. The coupling network includes phase shifter 62, 62', 64, 64', 66, 66', 68, and 68'. Unlike the Figure ~; 5A antenna~ all of the phase adjustments 61 r 63~ 65, 67 are ~: provided at the elements on the lower half of the array. As ~: 20 is k.nown to those famillar with the art, the ideal phase difference unction between elements in a pair, for example, pair 34, 34' of the Figure 5A antenna and pair 54, 54' of .
; . the Figure SB antenna is dependent on the space L between : the elements, as well as the`desired scan angle ~. For purposes of explaining the operatlon of the invention, i~ will be assumed that there is equal spacing L be~ween element pairs 34, 34' and 54, 54' so that there~is. idealIy the same : phase difference between signals suppliea to these elements for any particular antenna radiation angle.
~ 3i~r~ 23220 While the phase adjustments in Figures 5A and 5B
are illustrated as being arranged between the antenna element and the phase shifter, those familiar with the art will recognize ~hat the phase adjus~tments may be located at any point in the antenna coupling network provided the required phase difference exists at the antenna radiating element.
Likewise, those familiar with the art will recognize that the phase adjustment may have a phase magnitude e~ual to an odd integral multiple of one-half the smallest phase step of the digital phase shifter, and that th~ digital phase shiter may be appropriately controlled to remove any excess phase difference inisteps of its smallest bit. According to ; either arrangement, the elements are arranged in two groups, thosewith and those without the phase adjustments. The elements of any group always have a phase, with respect to the other elements in the same group, which is an integral multiple of the smallest phase shifter bit. The eleme~ts always have a phase, with respect to the eIements in the other group, which is an odd-integral multiple o one-half the smallest phase shifter bit.
: ~ Pigure 6 illustrates the ideal phase function for ~: ~ elements 34 and 34' of the Figure 5A antenna, which are the same as:the ideal phase functions for elements 54 and 54' of the Figure 5B antenna, because of the assumption of equal element spacing L. The ideal functions are identlcal to the ideal : functions for corresponding:elements l4 and 14'~of the : Figure l antenna.
The step functions in Flgure 6 illustrate the~digital phase approximations for phase shifters 44 and 44' to the 9-~
: ~
7Z~ 23220 ideal phase ~nction,which take into account the fixed phase difference introduced by phase adjustment 45. As compared to the graph of Figure 3, it will be seen that phase shifter 44' is switched at different intervals of scan angle ~ to S approximate the ideal function. This di~ference is the result of the presence of phase adjustment 45. The fact that phase shifter 44' is changed at different scan angles than phase shifter 44 results in a reduction in the magnitude of the phase error arising out of phase quantization. In this respect, it should be noted that the ~uantized phase function for each of the elements has the sam sense of displacement from the ideal function. Consequently, the difference between ; the actual quantized phase values is closer to the ideal phase difference. Figure 7 illustrates the phase quantization error ~' between elements 44 and 44' of the Figure 5A antenna, which is the same as the quantization error between eLements 54 and 54' o~ the Figure 5B antenna. From the graph, it may be seen that the maximum error is one-ha1f the smallest phase shifter bit or 22.5 not 45,which resuLted from the prior ~o art arrangement o~ Figure l.
Figure 8 illustrates apparatus for providing .
phase control signals t~ the phase~shifters of an array antenna. A beam selection device 90 provides output signals, for example logic signals repreaentative of the desired antenna beam pointing direction. These logic signals are i provided~as alddress inputs to read-only memories 92, 94, 96, and 98 (ROM's). The read-on~y memories are each programmed to provide the phase-shift control signals to one of the phase shifters of the array. In accordance with the invention, ~: :
~la~
~ ~ 23220 the memories must be progra~ned to take into account the presence of the phase adjustments in the antenna coupling network. It will be recognized that the required phase control signals may be provided by other devices, such as programmed microprocessors or special purpose computer circuits.
Figure 9 illustrates an application Oæ the invention to an antenna system wherein coupling means 75 are provided ~or interconnecting the element groups 72, 72', 74, 74', 76, 76', 78, and 78' of the array to varuous signal input ports 77 according to the prior U. S. Patent No. 4,041,501 to Frazita, et al. The coupling netowrk 73 connects trans-mitter 71 with ports 77 and includes phase s~ifters ~2, 82', 84, 84', 86, ~6', 88, and 88' as well a~ phase adjus~ments 81, 83, 85, and 87. The use o~ the present invention is of par~icular advantage in this type o array, because the large effective element spacing d', ~hich results from the use o ; the element intercouplin~ network, renders the antenna more susceptible to phase quntization pointing errors than con-ventional phased array antannas with a phase shifter for each individual element.
Computer calculations of antenna pointing errors for an antelma o~ the type illustrated in Figure 9 having 24 4 bit phase shifters have been mada. For the antenna without the phase adjustments according to the 1nvention,a2sigma pointing error of 0.011 deyrees was calculated. When phase adjus1~ments on both sides of the array center, in the configuration of Figure 5~, are provided the 2 sigma pointing ,: :
~11 :
~ {~ 23220 error from phase quantizatiorl is reduced approximately to 0.004 degrees. Phase adjustments on only one sidP of the array center, in the configuration of Figure 5B xeduced the
2 sigma pointing error to approximately 0.005 degrees.
The pointing error experienced in an actual system naturally depends on other factorslincluding the efects of dynamic beam steering and receiver bandwidth characteristics.
It should be noted that ~or any particular array having an odd or even number of elements or element groups, the phase adjustments may be provided on alternate elements or groups ~s shown in Figures 5A and 9 or on the elements to one side of the array center as shown in Figure 5B.
Those skilled in the art will recognize that the technique according to the invention results in a phase error between elaments in a pair which is always less than one-half the smallest step o~ the digital phase shifter.
While the invention is most easily explained in terms of antenna element pairs which are s~mmetrically located in a linaar or planar array, those familiar with the art will recogniæe that the invention may ba applied to randomly located element groups, or randomly located element pairs on plane or curved arrays and still achieve some of the objectives o~ the invention. The invention can easily be adapted to antennas which scan i~ more than one angular direction.
Such applications and their effects can be studied easily with the aid of a digital computer using formulas well known to those skilled in the art. It should also be recognized that although the speci~ication and elai~.s re~er primarily to transmlttinq antennas, such antennas are reciprocal, and the invention is e~ually applicable to receiving antennas.
~12 ::
The pointing error experienced in an actual system naturally depends on other factorslincluding the efects of dynamic beam steering and receiver bandwidth characteristics.
It should be noted that ~or any particular array having an odd or even number of elements or element groups, the phase adjustments may be provided on alternate elements or groups ~s shown in Figures 5A and 9 or on the elements to one side of the array center as shown in Figure 5B.
Those skilled in the art will recognize that the technique according to the invention results in a phase error between elaments in a pair which is always less than one-half the smallest step o~ the digital phase shifter.
While the invention is most easily explained in terms of antenna element pairs which are s~mmetrically located in a linaar or planar array, those familiar with the art will recogniæe that the invention may ba applied to randomly located element groups, or randomly located element pairs on plane or curved arrays and still achieve some of the objectives o~ the invention. The invention can easily be adapted to antennas which scan i~ more than one angular direction.
Such applications and their effects can be studied easily with the aid of a digital computer using formulas well known to those skilled in the art. It should also be recognized that although the speci~ication and elai~.s re~er primarily to transmlttinq antennas, such antennas are reciprocal, and the invention is e~ually applicable to receiving antennas.
~12 ::
Claims (12)
1. A phased array antenna system, comprising:
an aperture having a plurality of antenna element pairs, the elements of each pair being oppositely located with respect to a plane passing through said aperture;
and coupling means for supplying wave energy signals to said elements, said coupling means including digital phase shifters for varying the phase of said wave energy signals in discrete phase steps, the phase length of said coupling means being selected so that wave energy signals supplied to the elements in each pair have a phase-difference which is always approximately an odd-integral multiple of one-half the smallest phase step of said phase shifters.
an aperture having a plurality of antenna element pairs, the elements of each pair being oppositely located with respect to a plane passing through said aperture;
and coupling means for supplying wave energy signals to said elements, said coupling means including digital phase shifters for varying the phase of said wave energy signals in discrete phase steps, the phase length of said coupling means being selected so that wave energy signals supplied to the elements in each pair have a phase-difference which is always approximately an odd-integral multiple of one-half the smallest phase step of said phase shifters.
2. A phased array antenna system as specified in claim 1 wherein said plane passes through the center of said aperture and wherein the elements of each of said pairs are symmetrically located on said aperture with respect to said plane.
3. A phased array as specified in claim 2 wherein said phase shifters are responsive to phase control signals and wherein there are provided means for supplying phase control signals to said phase shifters to cause said coupling means to supply wave energy signals to said elements with a phase which is approximately a predetermined function, for each element, of the desired radiation angle of said array.
4. A phased array as specified in claim 3, wherein for any desired radiation angle the phase of wave energy signals supplied to each element in an element pair is less than one-half said smallest phase step from said predetermined function, and displaced in the same sense from said function, whereby the value of the difference of phase between wave energy signals supplied to the elements in a pair is within one-half of said smallest phase step from the value of the difference between said functions for said elements.
5. A phased array antenna comprising: a plurality of radiating elements arranged on an aperture plane on opposite sides of a central line on said place formed by the intersection of a perpendicular plane, said elements being arranged in pairs, each element in a pair being symmetrically located with respect to said perpendicular plane; coupling means, including a plurality of digital phase shifters responsive to phase control signals for varying the phase of wave energy signals supplied to said elements in discrete steps, for supply-ing wave energy signals to said elements, said coupling means supplying wave energy signals to the elements in each pair with a phase difference equal to an odd-integral multiple of one-half the smallest of said phase steps; and control means for supplying said phase control signals to said phase shifters to vary the phase supplied to said elements to approximate a computed phase value for each element, said computed phase value being a function of the desired radiation angle from said perpendicular plane.
6. A phased array antenna as specified in claim 5 wherein said coupling means supplies wave energy signals to each element with a phase which is different from the phase of wave energy signals supplied to at least one adjacent element by an odd-integral multiple of one-half of said smallest phase step.
7. A phased array as specified in claim 5 wherein said coupling means supplies wave energy signals to each element on one side of said line with a phase which is an integral multiple of said smallest phase step with respect to any other element on the same side of said line.
8. In a phased array antenna system having an aperture comprising an array of radiating elements and means for coupling wave energy signals to said elements, said coupling means including digital phase shifters for varying the phase of wave energy signals supplied to said elements in selected discrete phase steps, the improvement wherein said array includes first and second element groups, and said coupling means supplies wave energy signals to each of said elements in said first group with a phase with respect to a selected element in said first group which is approximately an integral multiple of the smallest step of said phase shifters, and wherein said coupling means supplies wave energy signals to each of said elements in said second group with a phase with respect to said selected element which is approximately an odd-integral multiple of one-half the smallest step of said phase shifters.
9. The improvement specified in claim 8 wherein said elements are arranged along a line and wherein said first group comprises alternate elements along said line.
10. The improvement specified in claim 8 wherein said elements are arranged along a line and wherein said first group comprises elements on one side of the center of said line.
11. In a phased array antenna wherein a plurality of antenna elements are arranged on an aperture, wherein there is provided a coupling network for coupling supplied wave energy signals to said elements, said network including a plurality of digital phase shifters responsive to phase control signals for varying the phase of wave energy supplied to said elements in discrete phase steps and wherein there is provided means for generating said phase control signals to cause said coupling means to supply wave energy signals to said elements with a phase which approxi-mates an ideal phase function of a desired radiation angle for each element, said ideal phase function being selected to cause reinfrocement of radiation from said elements in said desired radiation angle, the improvement wherein the phase lengths of said coupling means and said phase functions are selected to cause the phase difference between signals supplied to the elements in selected element pairs to be within one-half of the smallest phase step from the difference between said phase functions for the elements in said element pairs.
12. The improvement of claim 11 wherein said selected element pairs comprise elements symmetrically located with respect to the center of said array.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US872,525 | 1978-01-26 | ||
| US05/872,525 US4188633A (en) | 1978-01-26 | 1978-01-26 | Phased array antenna with reduced phase quantization errors |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1107390A true CA1107390A (en) | 1981-08-18 |
Family
ID=25359748
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA316,101A Expired CA1107390A (en) | 1978-01-26 | 1978-11-09 | Phased array antenna with reduced phase quantization errors |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4188633A (en) |
| JP (1) | JPS54104264A (en) |
| AU (1) | AU519114B2 (en) |
| CA (1) | CA1107390A (en) |
| GB (1) | GB2013407B (en) |
Families Citing this family (27)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ATE45058T1 (en) * | 1984-03-24 | 1989-08-15 | Gen Electric Co Plc | ANTENNA BEAM SHAPING NETWORK. |
| CA1238713A (en) * | 1984-06-04 | 1988-06-28 | Alliedsignal Inc. | Antenna feed network |
| US4876548A (en) * | 1986-12-19 | 1989-10-24 | Hazeltine Corp. | Phased array antenna with couplers in spatial filter arrangement |
| CN102412441A (en) * | 2011-09-02 | 2012-04-11 | 中国电子科技集团公司第十研究所 | Vector averaging calibration method for phased-array antenna |
| US8848772B2 (en) * | 2012-06-21 | 2014-09-30 | Intel Corporation | Device, system and method of phase quantization for phased array antenna |
| CN102810742B (en) * | 2012-08-01 | 2015-03-04 | 四川九洲电器集团有限责任公司 | Method for improving phased array beam-pointing accuracy |
| US9930592B2 (en) | 2013-02-19 | 2018-03-27 | Mimosa Networks, Inc. | Systems and methods for directing mobile device connectivity |
| US9179336B2 (en) | 2013-02-19 | 2015-11-03 | Mimosa Networks, Inc. | WiFi management interface for microwave radio and reset to factory defaults |
| WO2014138292A1 (en) | 2013-03-06 | 2014-09-12 | Mimosa Networks, Inc. | Enclosure for radio, parabolic dish antenna, and side lobe shields |
| US9130305B2 (en) | 2013-03-06 | 2015-09-08 | Mimosa Networks, Inc. | Waterproof apparatus for cables and cable interfaces |
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| US9191081B2 (en) | 2013-03-08 | 2015-11-17 | Mimosa Networks, Inc. | System and method for dual-band backhaul radio |
| US9295103B2 (en) | 2013-05-30 | 2016-03-22 | Mimosa Networks, Inc. | Wireless access points providing hybrid 802.11 and scheduled priority access communications |
| US10938110B2 (en) | 2013-06-28 | 2021-03-02 | Mimosa Networks, Inc. | Ellipticity reduction in circularly polarized array antennas |
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| US9780892B2 (en) | 2014-03-05 | 2017-10-03 | Mimosa Networks, Inc. | System and method for aligning a radio using an automated audio guide |
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| US9923270B1 (en) | 2014-09-10 | 2018-03-20 | Raytheon Company | Beamsteering technique to minimize sidelobes due to phase quantization in a phased array antenna |
| US10263331B2 (en) | 2014-10-06 | 2019-04-16 | Kymeta Corporation | Device, system and method to mitigate side lobes with an antenna array |
| US10749263B2 (en) | 2016-01-11 | 2020-08-18 | Mimosa Networks, Inc. | Printed circuit board mounted antenna and waveguide interface |
| US11251539B2 (en) | 2016-07-29 | 2022-02-15 | Airspan Ip Holdco Llc | Multi-band access point antenna array |
| US10511074B2 (en) | 2018-01-05 | 2019-12-17 | Mimosa Networks, Inc. | Higher signal isolation solutions for printed circuit board mounted antenna and waveguide interface |
| WO2019168800A1 (en) | 2018-03-02 | 2019-09-06 | Mimosa Networks, Inc. | Omni-directional orthogonally-polarized antenna system for mimo applications |
| US11289821B2 (en) | 2018-09-11 | 2022-03-29 | Air Span Ip Holdco Llc | Sector antenna systems and methods for providing high gain and high side-lobe rejection |
| CN113238101A (en) * | 2021-05-11 | 2021-08-10 | 深圳市中天迅通信技术股份有限公司 | Four-in-one feed coupling mobile phone antenna |
| CN114553334B (en) * | 2022-04-28 | 2022-07-22 | 浩泰智能(成都)科技有限公司 | Phased array antenna pointing error measurement method, system, terminal and device |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3387301A (en) * | 1966-03-31 | 1968-06-04 | Blass Antenna Electronics Corp | Antenna array employing an automatic averaging technique for increased resolution |
| US3999182A (en) * | 1975-02-06 | 1976-12-21 | The Bendix Corporation | Phased array antenna with coarse/fine electronic scanning for ultra-low beam granularity |
-
1978
- 1978-01-26 US US05/872,525 patent/US4188633A/en not_active Expired - Lifetime
- 1978-11-09 CA CA316,101A patent/CA1107390A/en not_active Expired
- 1978-11-15 GB GB7844668A patent/GB2013407B/en not_active Expired
- 1978-11-16 AU AU41643/78A patent/AU519114B2/en not_active Expired
- 1978-12-26 JP JP16445778A patent/JPS54104264A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0331001B2 (en) | 1991-05-02 |
| GB2013407B (en) | 1982-06-16 |
| GB2013407A (en) | 1979-08-08 |
| AU519114B2 (en) | 1981-11-05 |
| US4188633A (en) | 1980-02-12 |
| AU4164378A (en) | 1979-08-02 |
| JPS54104264A (en) | 1979-08-16 |
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